Process of coating



Patented July 14, 1942 moonss OFQCOATING Elvin M. Bright, Dayton, Ohio,assignor m Plastics Patents Trust, Dayton, Ohio, a trust No Drawing.

Application September 19, 1939, Serial No. 295,645

6 Claims. (01. 117-102) This invention relates to a plastic moldingmaterial and a nitrocellulose coating applied thereto. This is acontinuation in part of my copending application Serial No. 147,355filed June 9, 1937, for Plastic molding material.

An object of this invention is to produce an article from plasticmolding material suitably coated, that has great tensile strength, ischeap; but at the same time beautiful in appearance.

Another object of this invention is to subject the article fr'eshlycoated with nitrocellulose material to a solution having attraction forthe solvent used in dissolving the nitrocellulose material.

' Another object of this invention is to subject the coating to theinfluence of hygroscopic material, that is, a material thatihasattraction for moisture or water; but which does not penetrate thenitrocellulose material.

Another object of this invention is to subject the coating to a solutionhaving solvents therein common to the solvent of the nitrocellulosematerial and to wateror moisture without being a solvent for thenitrocellulose material.

Another object of this invention is to maintain the optimum osmotic,pressure in the freshly applied coating material.

Another object of this invention is to drain the I solvent used indissolving the nitrocellulose ma terial. in the fluid state from thefreshly applied coating.

Another object of this invention is to use a solution having anattraction for the solventused in dissolving the coating material, whichsolution has its attraction controlled so as to produce the optimumosmotic pressure in the freshly applied coating.

Other objects and advantages reside in the proportion of theingredients, the combination thereof and the mode of combining, as willbecome more apparent from the following description.

The nature of this invention is such that no drawings are deemednecessary.

The process of coating an article disclosed herein was developed bycoating an article molded from a plastic molding material disclosed inmy United States Letters Patent No. 2,152,867 for Game. That being thecase, the-process will be described in connection with an article moldedfrom the plastic molding material, which article is claimed in theaforementioned patent. It is expressly understood that this process isapplicable to coating numerous other articles, whether or not a unitarybond is produced between the article and the coating. This process hasbeen lected that is also a solve'nt'for the surface of the article to becoated. When the solvent for the nitrocellulose material that is commonto the material from which the article is coated is used, it usuallyresults in a strong bond between the coating and the article. This isvery desirable, so that in the event the coating is cracked, wornthrough, marred or mutilated, the coating will not drop oil? as a shellfrom the article. When the coating is bonded to the article, in theevent it is injured the bond will prevent the coating from peeling ordropping off of the article.

The available solvents that are satisfactory may all be classed ashighly volatile solvents, in that the solvents have a very low boilingpoint, especially if the pressure is reduced. The solvents evaporatevery rapidly under normal atmospheric conditions. As is well known tothose skilled in the art, rapid evaporation results in the reduction oftemperature. Furthermore, as the solvents pass out of thesurface of thefreshly coated article, the osmotic pressure within the article isreduced beyond the optimum osmotic pressure, causing the solvent to boilor gasify within the coating; thereby forming pinholes and blisters inthe surface, which are very objectiona e. I

The solvent used in dissolving the nitrocellulose material need notnecessarily be removed by evaporation. Instead, it may be drained fromthe coating into an extraction solution having an attraction for thesolvent, so that the solventflows as a liquid from the coating into thesolution without evaporation. However, in the event the difference inosmotic pressureat the surface is solvent within the coating. Instead ofcyclically dipping the article into a solution having an attraction forthe solvent and then arresting the escape of the solvent during theredistribution terial.

holes, blisters and the like.

of the solvent withinthe coating, an optimum osmotic pressure may bemaintained within the coating. Optimum osmotic. pressure," as usedherein and in the appended claims, is used to designate the condition atwhich the solvent is drained most rapidly as a liquid from the coatingwithout evaporation. In other words, it is used to designate thegreatest osmotic pressure difference possible without evaporation of thesolvent within the coating. The optimum osmotic pressure may be obtainedby adding to the solution used in attracting the solvent, sufl'icientsolvent so that the rate at which the solvent is withdrawn from thecoating does not result in evaporation of the solvent within thecoating. The conditions producing optimum osmotic pressure vary withchanges in temperature, changes in ratio of solvent to coating material,changes in thickness of coating applied, changes in the tation. Thesolvent may consist of- Sixty percent (60%) acetone, Twenty-five percentisopropyl acetate and Fifteen percent (15%) anhydrous isopropanol,

similar to a compound sold under the trade name Isotone and whichwillhereinafter be referred to as Isotone. The Isotone solvent found innitrocellulose coating has an effect upon the outer surface of themolding material used in molding the article, which, results in a betterouter surface being formed immediately inside the nitrocellulosecoating. 1 Articles coated with nitrocellulose material for some reasonare more resilient and seem more lively than articles that have not beencoated. It has been found upon the removal of the nitrocellulose coatingfrom an article made from the plastic molding material described inUnited States Letters Patent No. 2,152,867 that. the outer surface ofthe molding material has evidently been changed by the solvent used indissolving the nitrocellulose ma- It seems that when the article isdipped in the nitrocellulose material dissolved in Isotone, some of theIsotone enters the outer surface of the molding material, which causesthis outer surface of the moldingmaterial to undergo a change. Thischange in the'outer surface of the molding material improves some of thecharacteristics of the article.

The freshly coated article is now ready to be dipped into a solutionhaving an attraction for the solvent used in dissolving thenitrocellulose material. The nitrocellulose material should be insolublein the solution which should have no physical and no chemical effectupon the nitrocellulose material.

Gasoline has been used to withdraw a partof the solvent used indissolving nitrocellulose material, as shown by the prior art. In thepatent to Hampton No. 1,946,208 granted February 6, 1934, gasoline wassuggested for withdrawing some of the a solvent; but Hampton found itnecessary to subject the article to an extremely low temperature over along period of time in order to avoid excessive evaporation, causing pinIn the patent to Bright No. 2,152,867 supra, gasoline was used forwithdrawing some of the solvent cyclically. Both Hampton and Bright, asdisclosed in their patents,

could not use gasoline without afterwards retarding evaporation.

In the process as illustrated, a freshly coated article is dipped intogasoline, which gasoline has been diluted sufliciently with the solventof the coating material to obtain the optimum osmotic pressure, whichpermits withdrawal of the solvent as rapidly as possible without causingevaporation or boiling of the solvent remaining in the coating. Thisprocess permits the dipping of the freshly coat'ed article into adiluted solution of gasoline, where the article may remain until thesolvent has been removed sufliciently to permit the removal of thefreshly coated article into normal atmospheric conditions.

By this process the solvent used in dissolving the nitrocellulosematerial is drained from the article as a liquid, instead ofevaporation, as used in part of the treatment disclosed in the patent toHampton and the above identified patent to Bright.

In the event condensation should form upon the surface of the freshlycoated article before it is submerged in the diluted gasoline, thecondensation if not removed will blemish the surface of the article.This difliculty caused by condensation may be overcome by subjecting thefresh coating to the influence of a suitable hygroscopic material. Thismay be accomplished by dipping the freshly coated article into thegasoline solution having added thereto a suitable hygroscopic material,such as alcohol. The gasoline attracts or withdraws some of the solventused in dissolving the nitrocellulose material and the alcohol absorbsany condensation that may have accumulated upon the surface of thefreshly coated article. It has been found that one gallon of alcoholadded to forty gallons of gasoline, or whatever other solution is usedfor withdrawing the solvent of the nitrocellulose material, givesexcellent results.

Although the preferred embodiment has been described, it will beunderstood that within the purview of this invention various changes maybe made in the form, details, proportion and ingredients, whichgenerally stated consist in a material capable of carrying out theobjects set forth, in the combination of ingredients and method ofcombination as disclosed and defined in the appended claims.

Having thus described my invention, I claim:

1. The method of coating an article with a coating material, said methodincluding the steps of dipping the article into the coating materialdissolved by a solvent that is highly volatile at ordinaryatmospheric'temperatures, and subsequently dipping the freshly coatedarticle into an extraction olution having an attraction for the solventused in dissolving the coating material, in which solution said coatingmaterial is practically insoluble, said solution having added thereto asufiicient quantity of the aforementioned solvent for the coatingmaterial to reduce the attractionof the solution for the solvent toproduce optimum osmotic pressure conditions within the coating duringthe curing of the coating.

2. The method of coating an article with a coating material, said methodincluding the steps of dipping the article into the coating materialdissolved by a solvent that is highly volatile .at ordinary atmospherictemperatures and dipping the freshly coated article into an extractionsolution having an attraction for the solvent used in dissolving thecoating material, in which solu- 2,289,537 a tion said coating materialis practically insoluble, said solution having added thereto a smallquantity of the aforementioned solvent so as to reduce the attraction ofthe solution for the solvent, so as to maintain the osmoticpressuresufflciently uniform to cause the solvent to flow in a liquidstate at ordinary atmospheric temperatures from the coating materialinto the solution.

3. The method of coating an article with a coating material, said methodincluding the steps of dipping the article into the coating materialdissolved by a solvent that is highly volatile at ordinary atmospherictemperatures and subjecting the freshly coated article to the influenceof an extraction fluid medium having an attraction for the solvent usedin dissolving the coating material, said fluid medium having addedthereto a quantity of the solvent for the coating material to dilute thefluid medium so as to maintain the osmotic pressure sufliciently uniformto maintain the solvent in the fluid state at ordinary. atmospherictemperatures while escaping from the coating material into the fluidmedium.

4. The method of coating an article with nitrocellulose material, 'themethod including the steps of dipping the article into nitrocellulosematerial dissolved in a solvent that is highly volatile at ordinaryatmospheric temperatures especially w en the pressure is reduced bywithdrawal of the solvent from the coating, and dipping the freshlycoated article into an extraction fluid medium having an attraction forthe solvent used in dissolving the nitrocellulose material, said fluidmedium failing to materially penetrate the nitrocellulose coating, saidmedium being diluted by the addition of the solvent used in dissolvingthe nitrocellulose material so as to control the attraction ofsaidsolution for the solvent so as to cause the solvent to escape 3 atordinary atmospheric temperatures from the nitrocellulose coating intothe solution. a

5. The method of coating an article with nitrocellulose material,including the steps of dipping the article into nitrocellulose materialdissolved by a suitable solvent including acetone, isopropyl acetate andanhydrous iscpropanol, which solvent is highly volatile at ordinaryatmospheric temperatures especially when the pressure is reduced bywithdrawal'of the solvent from the coating, and subsequently dipping thefreshly coated article into gasoline having added thereto, acetone,isopropyl acetate, anhydrous isopropanol and alcohol, so as to reducethe attraction of the gasoline for the solvent, so as to cause thesolvent to flow in a liquid state at ordinary atmospheric temperaturesfrom the coating material into the gasoline.

6. The method of coating an article with nitrocellulose material, saidmethod including the steps of dipping the article into nitrocellulosematerial dissolved in a suitable solvent that is highly volatile atordinary atmospheric temperatures and subjecting the freshly coatedarticle to the influence of anextraction fluid solution having anattraction for the solvent used in dissolving the nitrocellulosematerial, said fluid solution failing to materially penetrate thenitrocellulose coating and having added thereto a quantityof theaforementioned solvent for the nitrocellulose material also failing tomaterially penetrate the nitrocellulose coating, said solvent reducingthe attraction of said extraction fluid solution for the solvent used indissolving the-nitrocellulose material, so as to cause the solvent toescape at ordinary atmospheric temperatures from the coating" materialinto the solution without deleterious gasiflcation.

ELVIN M. BRIGHT. I

